Tub having structually strengthened rear wall and washing machine with the same therein

ABSTRACT

A tub having a structurally strengthened rear wall and a washing machine with the same therein are disclosed. A washing machine includes a bearing housing having a flange part and a tub part injection-molded with the bearing housing inserted into a wall thereof, the wall having a recessing part and a projecting part formed on an inner or an outer surface thereof along a circumferential direction, and a circumferential rib or a radical rib formed on the recessing part.

This application is continuation of application Ser. No. 11/413,113filed on Apr. 28, 2006 which is a continuation-in-part of applicationSer. No. 10/730,281 filed on Dec. 9, 2003 which is now U.S. Pat. No.7,418,843, which claims priority of Korean Patent Application10-2002-0078337 and 10-2003-0086841 filed in Korea on Dec. 10, 2002 andon Dec. 2, 2003, respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tub having a structurallystrengthened rear wall and a washing machine with the same therein, andmore particularly, to a tub injection-molded with a bearing housinginserted supporting a shaft to rotate a drum.

2. Discussion of the Related Art

In general, a drum type washing washes laundry by using a friction forcebetween a drum rotated by a driving power of a motor and the laundry ina state detergent, washing water, and the laundry are introduced intothe drum, shows almost no damage to, and entangling of the laundry, andhas pounding, and rubbing washing effects.

In the related art drum type washing machines, there are an indirectdrive type in which the driving power of the motor is transmitted to thedrum through a belt wound on a motor pulley and a drum pulleyindirectly, and a direct drive type in which the brushless DC (BLDC)motor is connected to the drum directly, to transmit the driving powerof the motor to the drum, directly.

The type in which the driving power of the motor is transmitted to thedrum, not directly, but indirectly through the motor pulley and the drumpulley, has much energy loss in the course of power transmission, andcauses much noise in the course of power transmission.

According to this, it is the present trend that use of the direct drivetype drum type washing machines with the BLDC motor is increasing, forsolving the problems of the indirect drive type drum type washingmachines. A related art direct drive type drum type washing machine willbe described with reference to FIG. 1, briefly. FIG. 1 illustrates alongitudinal section of a related art drum type washing machine.

Referring to FIG. 1, the related art drum type washing machine isprovided with a tub 2 mounted inside of a cabinet 1, and a drum 3rotatably mounted on a central part of an inside of the tub 2. There isa motor in rear of the tub 2, wherein a stator 6 is fixed to a rear wallof the tub, and a rotor 5 surrounds the stator 6, and is connected tothe drum 3 with a shaft passed through the tub.

Together with these, there is a metallic tub supporter between a tubrear wall and the stator having a shape almost the same with an outershape of the tub rear wall fixed to the tub rear wall in fastening thestator for supporting a load of the stator, and maintaining aconcentricity of the stator.

In the meantime, there are a door 21 mounted on a front part of thecabinet 1, and a gasket 22 between the door 21 and the tub 2.

There are a hanging spring 23 between an inside surface of an upper partof the cabinet 1, and an upper part of an outside circumferentialsurface of the tub 2, and a friction damper 24 between the insidesurface of a lower part of the cabinet 1, and a lower part of theoutside circumferential surface of the tub 2.

FIG. 2 illustrates a perspective outside view of the stator in FIG. 1,and FIG. 3 illustrates a perspective view of a sectional type core SCapplied to the stator in FIG. 2.

In a related art method for fabricating the stator core, a sheet ofmetal plate is pressed to form a unit core having tooth portions 151, abase part 150, and a round part 500 opposite to the tooth portions 151for forming fastening hole 500 a therein, the unit cores are stacked toform a unit core assembly, and the unit core assemblies are connected toeach other in a circumferential direction, to complete fabrication ofthe stator core, called the sectional type core SC.

The round part provides the fastening hole 500 a for fixing the stator 6to the rear wall of the tub, and enduring a fastening force of a bolt.

However, the method for fabricating the stator 6 by means of thesectional type cores SC has, not only a complicate fabrication process,but also loss of much material.

Therefore, even if a helical type core HC is favorable, in which a sheetof steel plate having the tooth portions 151 and the base part 150 isstacked turning in a helix, since it is required to bend the sheet ofmetal punched out in a form of a band into the helix, the helical typecore has a drawback in that the round part for fixing the stator to thetub can not be formed on an inner side of the core.

This is because, if the round part 500 is formed on the inner side ofthe core in fabrication of the helical core HC, a large width of thecore at a part having the round part formed thereon impedes bending ofthe core.

Therefore, currently, a stator structure is required, in which afunction the same with the round part of the sectional type core SC ismade to be carried out, not by the core itself, but by other part, foremploying the helical type core HC.

For reference, a reason why it is important to secure an adequaterigidity of the round part having the fastening hole formed in forfixing the stator to the tub is as follows.

The washing machine that rotates the drum directly by using the BLDCmotor has the stator mounted on a rear part of the tub, directly. In acase of the motor for a large capacity drum type washing machine withmore than 1.5 kg of stator net weight, and a spinning speed in a rangeof 600˜2000 RPM, it is liable that a bolt fastened part of the stator 6is broken due to the stator weight, vibration in the high speedrotation, and shaking and deformation of the rotor 5.

Particularly, in a case of the drum type washing machine, in which theBLDC motor is used, and the stator 6 is fixed to the tub rear wall,where an axis direction of the stator 6 is substantially parallel toground, the vibration generated in operation of the washing machinecauses intensive damage to the fastening part of the stator 6 to the tubrear wall.

Thus, an adequate rigidity of the round part having the fastening holeformed therein is very important in fixing the stator 6 to the tub.

In the meantime, in a trend a capacity of the drum type washing machinebecomes larger as the time goes by, there have been many problems, suchas even the tub to which the stator is fastened is damaged in a case thestator has a weight more than 1.5 kg in a structure the axis of thestator is parallel to the ground like the drum type washing machine.

Therefore, in order to prevent occurrence of the damage, in the relatedart structure, in general a metal tub supporter is lined, when a processfor fastening the tub supporter to the tub rear wall is required inaddition to an assembly line, that drops a productivity.

FIG. 4 illustrates a conventional tub 302, more specifically, an outersurface of the rear wall where the motor is mounted.

As shown in FIG. 4, a circumferential rib 311 and 312 is formed in acircumferential direction on the outer surface of the rear wall of thetub 302, and a radial rib 321 is also formed on the outer surface of therear wall in a radial direction. The farther the radial rib 321 is fromthe center of the rear wall, the lower the height thereof is. Thus, therear wall of the tub may have a problem in its strength and rigidity.Furthermore, the distance between the radial ribs is gradually gettingwider from the center thereof. Thereby, the strength of the rear wall ofthe tub is not high enough and it causes a structural-strength-relatedproblem in the farthest portion of the rear wall from the center.

Also, the thickness between the circumferential rib 311 formed nearer tothe center of the rear wall and the circumferential rib 312 formedfarther from the center is the same. Since the nearer portion to thecenter is more affected by the vibration of the shaft than the fartherportion, the nearer portion is needed to have much strength andrigidity. Nevertheless, the conventional washing machine fails to solvethe above problem.

Moreover, according to the conventional washing machine, thecircumferential rib 311 and 312 and the radial rib 321 are formedrelatively high to enhance the strength of the rear wall of the tub.However, the higher the ribs are, the more flexible the ribs are.Thereby, the strength or rigidity is not gained as high as structurallyrequired and it causes a structural-strength-related problem as well ashigh production cost.

Meanwhile, since the inner surface (not shown) of the rear wall of thetub is formed as a smooth surface without ribs, the reinforcement forthe strength is dependent on the ribs on the outer surface only. That isone of the reasons why the ribs on the outer surface are high in theconventional washing machine.

The capacity of the tub for holding wash water therein influences thecapacity of the washing machine. Here, the capacity of the tub isinfluenced by the position of the inner surface of the rear wall. Sincethe conventional rear wall of the tub described above has the innersurface thereof sided toward the drum, the conventional rear wall of thetub has a disadvantage that the tub has a small capacity.

Also, the overall thickness of the rear wall of the tub with the heightof the rib considered may affect the disposition of the other componentswithin the limited space of the cabinet.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a tub having astructurally strengthened rear wall and a washing machine with the sametherein that substantially obviates one or more problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a tub having astructurally strengthened rear wall and a washing machine with the sametherein, wherein the rear wall of the tub with a bearing housinginserted therein has a recessing part and a projecting part along acircumferential direction and a flange part of the bearing housing has arecessing part and projecting part corresponding with the recessing partand the projecting part of the rear wall.

Another object of the present invention is to provide a tub manufacturedby injection-molding process with a bearing housing inserted into themold, wherein the tub does not cause a problem due to stressconcentration especially in the place near to the outer end of theflange of the bearing housing.

A third object of the present invention is to provide a rear wall of atub having a recessing part and a projecting part thereon forreinforcing the strength and rigidity. Especially, the ribs are formedon the recessing part to maintain the predetermined overall thickness ofthe rear wall of the tub, such that the disposition of other componentsand the capacity of the tub are not affected.

A fourth object of the present invention is to help a drum to rotatesmoothly by thickening the circumferential rib nearest to the center ofthe rear wall and structurally strengthening the center portion affectedby the vibration of the shaft most, such that the shaft is supportedsecurely.

Recently, there have been demands for a washing machine with a largecapacity. Also, the demands for a tub having a structurally strengthenedrear wall have increased. Thus, the present invention is invented tosatisfy the demands and to provide a rear wall of a tub having noproblems of the related art in a washing machine with a large capacity.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, awashing machine comprising a bearing housing having a flange part; and atub injection-molded with the bearing housing inserted into a wallthereof, the wall having a recessing part and a projecting part formedon an inner or an outer surface thereof along a circumferentialdirection, and a circumferential rib or a radial rib formed on therecessing part.

The wall of the tub, as shown in FIG. 1, is a rear wall in a frontloading type washing machine, and a vertical wall of a left side or aright side in a top loading type washing. The wall is a portion where abearing housing for supporting a shaft rotating a drum is inserted,regardless of any type of washing machines. The front loading typewashing machine is presented as an example as follows, and the presentinvention may be applied to any type of washing machines included in thescope of the present invention.

According to the present invention, the bearing housing and the tub maybe fastened securely, because the bearing housing is inserted into therear wall of the tub. In addition, since the bearing housing has theflange part, the strength and rigidity of the rear wall of the tub canbe enhanced by the flange part, and the tub and the bearing housing canbe connected securely.

Furthermore, the strength and rigidity of the rear wall can be moreenhanced, because the rear wall has the recessing part and theprojecting part. The recessing part and the projecting part can beformed on an inner surface or an outer surface of the rear wall.Preferably, the recessing part and the projecting part are formed on theboth of the inner and outer surface of the rear wall.

Here, a circumferential rib or a radial rib is formed on the recessingpart in a circumferential direction to structurally strengthen the wall.Preferably, the circumferential rib and the radial rib are formed.

The present invention is invented through a lot of experiments andcomputer aided engineering. The inventor is motivated to find a problemof crack caused in case that a circumferential rib is provided on thesame circumference as the circumference of an outer end of the flangepart of the bearing housing. The inventor found that the biggest reasonis the stress concentration on the end of the circumferential rib.

Therefore, it is preferred that the circumferential rib is spaced apartfrom an outer end of the flange part in a radial direction. That is, thecircumferential rib is preferred not to be provided on the samecircumference as the circumference of the outer end of the flange part.

Preferably, a circumferential rib or a radial rib is formed on theprojecting part on the same circumference of the outer end of the flangepart.

Especially, in case that the circumferential rib is provided on the samecircumference as the circumference of the outer end of the flange part,the circumferential rib or the radial rib is more necessarily providedon the projecting part.

In connection with the structural strength, the correlation between thepotion of the circumferential rib and the outer end of the flange partis found through many experiments and a process of trial and error, andthe above technical solution has the most preferable result out of thevarious trials.

Moreover, preferably, the flange part of the bearing housing has arecessing part and a projecting part corresponding with the recessingpart and the projecting part of the wall, respectively. It is morepreferable that the flange part has an embossing appearancecorresponding with the embossing appearance of the rear wall of the tubfor the recessing and the projecting parts.

At least one portion of the radial rib formed on the recessing part ofthe wall is inclined upwardly from the center of the wall. Especially,as far as the strength is concerned, it is preferable that the inclinedportion is a portion of the rear wall where the flange part is notinserted, since the portion where the flange part is inserted isreinforced enough by the flange part. That is, the farther outwardlyfrom the outer end of the flange part, the higher the radial rib is.

Since the flange part is inserted into the near portion of the rear wallfrom the center and the distance between the radial ribs is narrow, thecenter portion of the rear wall is structurally strengthened. Whereas,the other portions are not strengthened enough. Thus, the strength isreinforced by heightening the radial rib.

Preferably, the circumferential rib and the radial rib formed on therecessing part of the wall of the tub cross. In case that they do notcross, the inventor found through the experiments and computer aidedengineering that the stress is concentrated. Also, preferably, theheight of the circumferential rib and the height of the radial rib arethe same due to the same reason.

Since it is affected a lot by the vibration of the shaft, the innercenter portion of the rear wall of the tub should be structurallystrengthened. For that reason, the circumferential rib formed on therecessing part of the wall of the tub is provided in plural, and thecircumferential rib nearest to the center is thicker than the othercircumferential ribs.

The circumferential rib nearest to the center is formed in the samecircumference as a circumference of a boss for allowing a statorfastened thereto.

Preferably, the flange part has a circumferential rib, and morepreferably, the circumferential rib of the flange part is inserted intothe nearest circumferential rib of the tub to the center.

An object of the present invention is to provide a drum type washingmachine, which has an outer rotor type motor with a stator of whichmaterial and weight required for fabrication can be reduced, fabricationof which can be simplified, and secure mounting of which on the tub ispossible.

Other object of the present invention is to provide a drum type washingmachine, in which a tub can sustain weight and vibration of a BLDC motorfor a washing machine mounted on a tub wall directly, which motor has anet stator weight more than 1.5 kg, and variable rotational speed of0˜2000 RPM or over.

Another object of the present invention is to provide a drum typewashing machine, which can dispense with a tub supporter fasteningprocess from an assembly line, that can secure a supporting force of thetub rear wall to the stator, and simplifies an assembly process.

Further object of the present invention is to provide a drum typewashing machine, which enables a service man to carry out maintenance inrepair and replacement of components.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent to thosehaving ordinary skill in the art upon examination of the following ormay be learned from practice of the invention. The objectives and otheradvantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, the drum type washing machine includes a tub of plastic having awall for holding washing water therein and mounting a driving partthereon, a drum rotatably arranged inside of the tub, a shaft passedthrough the tub and connected to the drum for transmission of a drivingpower from a motor to the drum, at least one bearing for supporting theshaft, a bearing housing having a sleeve form of bearing supportingpart, and a stator fastening part extended in a radial direction fromthe bearing supporting part, wherein both of the bearing supporting partand the stator fastening part are inserted in a tub rear wall, whilestator fastening holes in the stator fastening part are exposed, a rotorengaged to a rear end part of the shaft to form the motor together withthe stator, and the stator mounted on the stator fastening part of thebearing housing with fastening members on an inner side of the rotor toform the motor together with the rotor, wherein the stator includes anannular helical type core having multiple layers formed by winding asteel plate having tooth portions and a base part in a helix startingfrom a bottom layer to a top layer, an insulator having the helical typecore encapsulated therein, a coil wound on the tooth portions, andfastening parts formed as a unit with the insulator, having fasteningholes projected toward an inside of the helical type core for fasteningthe stator to the bearing housing.

In other aspect of the present invention, there is provided a drum typewashing machine including a tub of plastic having a wall for holdingwashing water therein and mounting a driving part thereon, a drumrotatably arranged inside of the tub, a shaft passed through the tub andconnected to the drum for transmission of a driving power from a motorto the drum, at least one bearing for supporting the shaft, a bearinghousing having a sleeve form of bearing supporting part, and a statorfastening part extended in a radial direction from the bearingsupporting part, wherein both of the bearing supporting part and thestator fastening part are inserted in a tub rear wall, while statorfastening holes in the stator fastening part are exposed, a rotorengaged to a rear end part of the shaft to form the motor together withthe stator, and the stator mounted on the stator fastening part of thebearing housing with fastening members on an inner side of the rotor toform the motor together with the rotor, wherein the stator includes anannular helical type core having multiple layers formed by winding asteel plate having tooth portions and a base part in a helix startingfrom a bottom layer to a top layer, an insulator having the helical typecore encapsulated therein, a coil wound on the tooth portions, andfastening parts formed as a unit with the insulator, having three ormore than three fastening holes projected toward an inside of thehelical type core for fastening the stator to the bearing housing.

In another aspect of the present invention, there is provided a drumtype washing machine including a tub of a plastic having a wall forholding washing water therein and mounting a driving part thereon a drumrotatably arranged inside of the tub, a shaft passed through the tub andconnected to the drum for transmission of a driving power from a motorto the drum, at least one bearing for supporting the shaft, a bearinghousing having a sleeve form of bearing supporting part inserted in thetub rear wall, and a stator fastening part formed as a unit with thebearing supporting part extended from the bearing supporting partexposed to an outside of the tub, with stator fastening holes formed inan exposed part of the stator fastening part, a rotor engaged to a rearend part of the shaft to form the motor together with the stator, andthe stator mounted on the stator fastening part of the bearing housingwith fastening members on an inner side of the rotor to form the motortogether with the rotor, wherein the stator includes an annular helicaltype core having multiple layers formed by winding a steel plate havingtooth portions and a base part in a helix starting from a bottom layerto a top layer, an insulator having the helical type core encapsulatedtherein, a coil wound on the tooth portions, and fastening parts formedas a unit with the insulator, having fastening holes projected toward aninside of the helical type core for fastening the stator to the bearinghousing.

In further object of the present invention, there is provided a drumtype washing machine including a tub of a plastic having a wall forholding washing water therein and mounting a driving part thereon, adrum rotatably arranged inside of the tub, a shaft passed through thetub and connected to the drum for transmission of a driving power from amotor to the drum, at least one bearing for supporting the shaft, abearing housing having a sleeve form of bearing supporting part insertedin the tub rear wall, and a stator fastening part formed as a unit withthe bearing supporting part extended in a radial direction from thebearing supporting part exposed to an outside of the tub, with statorfastening holes formed in an exposed part of the stator fastening part,a rotor engaged to a rear end part of the shaft to form the motortogether with the stator, and the stator mounted on the stator fasteningpart of the bearing housing with fastening members on an inner side ofthe rotor to form the motor together with the rotor, wherein the statorincludes an annular helical type core having multiple layers formed bywinding a steel plate having tooth portions and a base part in a helixstarting from a bottom layer to a top layer, an insulator having thehelical type core encapsulated therein, a coil wound on the toothportions, and fastening parts formed as a unit with the insulator,having three or more than three fastening holes projected toward aninside of the helical type core for fastening the stator to the bearinghousing.

In still further object of the present invention, there is provided adrum type washing machine including a tub of plastic having a wall forholding washing water therein and mounting a driving part thereon, adrum rotatably arranged inside of the tub, a shaft passed through thetub and connected to the drum for transmission of a driving power from amotor to the drum, at least one bearing for supporting the shaft, abearing housing having a sleeve form of bearing supporting part, and astator fastening part extended in a radial direction from the bearingsupporting part, wherein both of the bearing supporting part and thestator fastening part are inserted in a tub rear wall, while statorfastening holes in the stator fastening part are exposed, a rotorengaged to a rear end part of the shaft to form the motor together withthe stator, and the stator mounted on the stator fastening part of thebearing housing with fastening members on an inner side of the rotor toform the motor together with the rotor.

In yet further aspect of the present invention, there is provided a drumtype washing machine including a tub of plastic having a wall forholding washing water therein and mounting a driving part thereon, adrum rotatably arranged inside of the tub, a shaft passed through thetub and connected to the drum for transmission of a driving power from amotor to the drum, at least one bearing for supporting the shaft, abearing housing having a sleeve form of bearing supporting part insertedin the tub rear wall, and a stator fastening part formed as a unit withthe bearing supporting part extended in a radial direction from thebearing supporting part exposed to an outside of the tub, with statorfastening holes formed in an exposed part, a rotor engaged to a rear endpart of the shaft to form the motor together with the stator; and thestator with a weight heavier than 1.5 kg mounted on the stator fasteningpart of the bearing housing with fastening members on an inner side ofthe rotor to form the motor together with the rotor.

In still yet further aspect of the present invention, there is provideda drum type washing machine including a tub having a wall for holdingwashing water therein and mounting a driving part thereon, and a sleeveform of bearing supporting part for supporting bearings, in which boththe tub and the bearing supporting part are formed as one unit, a drumrotatably arranged inside of the tub, a shaft passed through the tub andconnected to the drum for transmission of a driving power from a motorto the drum, at least one bearing inside of the bearing supporting partfor supporting the shaft, a rotor engaged to a rear end part of theshaft to form the motor together with the stator, and the stator mountedon the tub on an inner side of the rotor and an outer side of thebearing supporting part with fastening members, wherein the statorincludes an annular helical type core having multiple layers formed bywinding a steel plate having tooth portions and base part in a helixstarting from a bottom layer to a top layer, an insulator having thehelical type core encapsulated therein, a coil wound on the toothportions, and fastening parts formed as a unit with the insulator,having fastening holes projected toward an inside of the helical typecore for fastening the stator to the bearing housing.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram illustrating a conventional drum type washingmachine according to the related art.

FIG. 2 illustrates a perspective view of a related art stator.

FIG. 3 illustrates a perspective view of a sectional type core.

FIG. 4 is a diagram illustrating a conventional tub injection-moldedwith a bearing housing inserted therein.

FIG. 5 illustrates a longitudinal section of a direct drive, drum typewashing machine in accordance with a preferred embodiment of the presentinvention, schematically.

FIG. 6 illustrates an enlarged longitudinal sectional view of an ‘A’part in FIG. 5 of the drum type washing machine of the presentinvention.

FIG. 7 illustrates a cut away perspective view of a tub rear wall.

FIG. 8 illustrates a perspective view of the unitary bracket and bearinghousing in FIG. 6.

FIG. 9 illustrates a backside perspective view of FIG. 8.

FIG. 10 illustrates a section across a line I-I in FIG. 8.

FIG. 11 illustrates a perspective view of the stator in FIG. 6.

FIG. 12 illustrates a perspective view of the helical type core in FIG.11.

FIG. 13A illustrates a plan view of key parts of the stator in FIG. 11,and FIG. 13B illustrates a perspective view of key parts of the statorin FIG. 11.

FIG. 14 illustrates a perspective view of a stator in a driving part ofa drum type washing machine in accordance with another preferredembodiment of the present invention.

FIG. 15 illustrates a longitudinal section of a drum type washingmachine in accordance with another preferred embodiment of the presentinvention.

FIG. 16 is a diagram illustrating an outer surface of a rear wall of atub according to the present invention.

FIG. 17 is a diagram illustrating an inner surface of the rear wall ofthe tub in FIG. 16 according to the present invention.

FIG. 18 is a perspective view illustrating enlarged key parts of FIG.16.

FIG. 19 is a sectional view illustrating that a motor is mounted in thetub of FIG. 16.

FIG. 20 is a diagram illustrating an outer surface center portion of arear wall of a tub according to another embodiment of the presentinvention.

FIG. 21 is a diagram illustrating an inside of the tub in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 5 illustrates a longitudinal section of a direct drive, drum typewashing machine in accordance with a preferred embodiment of the presentinvention schematically, and FIG. 6 illustrates an enlarged longitudinalsectional view of an ‘A’ part in FIG. 5 of the drum type washing machineof the present invention.

FIG. 7 illustrates a cut away perspective view of a tub rear wall, FIG.8 illustrates a perspective view of the unitary bracket and bearinghousing in FIG. 6, FIG. 9 illustrates a backside perspective view ofFIG. 8, and FIG. 10 illustrates a section across a line I-I in FIG. 8.

FIG. 11 illustrates a perspective view of the stator in FIG. 6, FIG. 12illustrates a perspective view of the helical type core in FIG. 11, FIG.13A illustrates a plan view of key parts of the stator in FIG. 11, andFIG. 13B illustrates a perspective view of key parts of the stator inFIG. 11.

The drum type washing machine of the present invention, having a tub 2inside of a cabinet 1 for holding washing water, with a wall for fixinga driving part thereto, a drum 3 inside of the tub 2, a shaft 4connected to the drum 3 with a shaft for transmission of a driving powerfrom a motor to the drum 3, and a bearing for supporting the shaft 4,wherein the tub 2 is formed of a plastic, and includes a metal bearinghousing 7 at a central part of a rear wall of the tub 2 both forsupporting the bearings at both ends of an outside circumferentialsurface of the shaft 4 and fastening the stator 6.

The bearing housing 7 is formed of an aluminum alloy and the like, andintegrated with the tub rear wall by inserting the bearing housing 7 ina mold in an injection molding of the tub 2 of plastic.

In the meantime, referring to FIG. 6, the bearing housing 7 includes abearing supporting part 7 a of a sleeve form for supporting thebearings, a stator fastening part 7 b formed as a unit with the bearingsupporting part 7 a extended form a rear end of the bearing supportingpart 7 a in a radial direction, and stator fastening holes 700 b in thestator fastening part 7 b, wherein both the bearing supporting part 7 aand the stator fastening part 7 b are inserted in the tub 2 rear wall,when only the stator fastening holes 700 b are exposed.

Referring to FIGS. 8 and 9, the stator fastening part 7 b, extended fromthe sleeve form of bearing supporting part 7 a in the radial directionoutwardly, includes stepped areas 70 b-1 each having at least one stepin the outward extension in a direction of the outward extension, andflat areas 70 b-2 each between adjacent stepped areas 70 b-1, whereinthe stepped areas 70 b-1 and the flat areas 70 b-2 are connected to eachother, respectively.

That is, the stator fastening part 7 b includes the stepped areas 70 b-1each having steps as the stepped area 70 b-1 extends in an outwardradial direction, and flat areas 70 b-2 between the stepped areas 70b-1, wherein each of the areas 70 b-1 extended from an upper end of thebearing supporting part 7 a in the outward radial direction is bent downat preset intervals as the stepped area 70 b-1 extends in the outwardradial direction, and each of the areas 70 b-2 connected to a lower endof the bearing housing 7 is flat.

There is a resin stuffing groove 750 a around the upper part of thebearing housing 7 for enhancing a bonding force with the tub 2 in theinsert injection molding.

Referring to FIGS. 7 and 8, there is a positioning hole 710 b formedadjacent to a stator fastening hole 700 b of the stator fastening part 7b in correspondence to a positioning projection on the stator 6.

Referring to FIG. 7, there is a boss 200 at a part of the tub rear wallopposite to each of the stator fastening holes 700 b for preventing thestator fastening part 7 b from coming into direct contact with thestator 6, thereby preventing an insulator of the stator 6 from beingbroken due to a fastening force applied thereto in mounting the stator6.

It is also preferable that the stator fastening part 7 b has acircumferential rib 720 b at a position spaced a distance from an axisof the bearing supporting part 7 a for increasing a bonding force withthe plastic in the injection molding of the tub 2. Though it ispreferable that there are fastening bosses 70 b each with a statorfastening hole 700 b on the rib 720, it is not necessarily required toform the fastening holes 700 b on the rib 720 b.

In addition to this, there are circumferential and radial reinforcingribs 201 on a region excluding the bearing housing stepped area of thetub rear wall for reinforcing the tub rear wall.

In the meantime, different from the foregoing stator fastening part 7 b,the stator fastening part 7 b may be an extension from the sleeve formof the bearing supporting part 7 a the same with the foregoing statorfastening part 7 b, but separated at regular intervals in acircumferential direction to form a plurality of separated radialsegments.

Referring to FIGS. 6 and 7, the bearing housing 7 of metal has a step 8a in an inside circumferential surface for supporting, and preventingthe bearings 600 a on the inside circumferential surface from breakingaway from the bearing housing 7.

A front part of the shaft 4 is fixed to a spider 10 in a rear wall ofthe drum 3, and a section of the shaft 4 from an exposed part in rear ofthe spider 10 to a front bearing 600 a has a brass bushing 11 press fitthereon for preventing the shaft 4 from rusting, with a sealing member12 fitted on an outside surface of the bushing 11 for preventinginfiltration of water toward the bearing.

The shaft 4 has the rotor 5 of the direct drive motor mounted at acenter of rear end thereof, on an inner side of which the stator 14 ispositioned, that is mounted on the tub rear wall to form the directdrive motor together with the rotor 5.

Referring to FIG. 6, the rotor 5, formed of steel plate, has acircumferential bent part with a seating surface 130 for seating magnetsM placed on an inside surface of a side wall 13 b extended forward froman edge of a rear wall of the rotor 5, and a hub 132 in a center part ofthe rear wall 13 a having through holes for passing fastening members 15a, such as bolts, in mounting the rotor 5 on the shaft 4.

It is preferable that the rotor 5 is formed by pressing.

The rotor 5 has a plurality of radial cooling fins 133 around the hub132 for blowing air toward the stator 6 when the rotor 5 rotates, tocool down heat from the stator 6. Each of the cooling fins 133 has alength in the radial direction.

The cooling fin 133 is formed by lancing to be bent at 90° from the rearwall to direct an opened side of the rotor 5, and a through hole 134formed in the lancing serves as an air hole.

The rotor 5 has embossing 135 between adjacent cooling fins 133 of therear wall 13 a for reinforcing the rotor 5, and drain holes 136 in theembossing 135.

The rotor 5 has fastening holes 137 for fastening a connector 16 engagedwith a rear end part of the shaft 4 in rear of a rear bearing 600 b bymeans of serration, and positioning holes 138 for positioning theconnector in mounting the connector on the shaft 4, both of whichfastening holes 137 and positioning holes 138 are formed around thethrough hole 131 in the hub 132 at regular intervals.

The connector 16 is formed of plastic having a vibration mode differentfrom the rotor 5 of steel plate, and serves as a bushing for the rotor,too. The connector 16 has serration 164 fit to the serration 400 in therear end part of the shaft 4.

The tub rear wall has a hub part for putting the bearing supporting part7 a of the bearing housing 7 therein in the injection molding of the tub2.

According to this, the present invention permits to dispense with thetub supporter which is essential in the related art, to reduce assemblyman power in an assembly line, and improve a productivity.

That is, the present invention permits to dispense with the tubsupporter, which is a separate part having an almost same outside shapewith the tub rear wall, fixed to, and holds the tub rear wall inmounting the stator 6, and maintains a concentricity of the stator 6.

Referring to FIG. 11, the stator 6 includes a helical type core HC, aninsulator 144 having the helical type core HC encapsulated therein, acoil wound around tooth portions 151 of the helical type core HC, andfastening parts 143 molded as a unit with the insulator 144 projectedtoward an inside of the helical type core HC from three, or more thanthree places, and in general weighs more than 1.5 kg as the capacity ofthe drum type washing machine becomes larger.

The helical type core HC has multiple layers formed by winding a steelplate having the tooth portions and the base part in a helix startingfrom a bottom layer to a top layer, with the tooth portions 151projected outwardly in a radial direction from the base part. The basepart 150 has recesses 152 for reducing stress in the winding of thehelical type core.

The multiple layers of the helical type core HC are fastened with rivets153 passed through through holes in the base part 150. A starting partand an end part of the helical type core HC may be welded at the baseparts 150 in contact thereto. The recess 152 in the base part 150 may berectangular, trapezoidal, or an arc.

Referring to FIGS. 13A and 13B, in the stator 6 having three or morethan three fastening parts 143 formed as a unit with the insulator so asto be projected in a radial direction toward inside from the insidecircumferential surface of the helical type core, each of the fasteningparts 143 is formed to meet a condition of a≧b, where “a” denotes alength of the tooth portion 151 from an outer edge of the base part 150,and “b” denotes a distance from an inner edge of the base part 150 to acenter of the fastening hole 143 a.

The fastening part 143 has a height greater than 20% of a total corestack height, and preferably equal to the total core stack height.

The fastening part 143 has at least one cavity 143 c for dampingvibration at the time of motor driving, and a positioning pin 143 b fitto the positioning hole 710 b in the stator fastening part exposed in astate inserted in the tub rear wall.

In the meantime, there is a metal tube 143 p or a spring pin forciblyinserted in the fastening hole 143 a of the fastening part 143.

The operation of the driving part of the drum type washing machine ofthe present invention will be described.

Under the control of a controller (not shown) attached to a panel fordriving the motor, if current flows to the coils 142 in the stator 6 insuccession, to rotate the rotor 5, the shaft 4 engaged with theconnector 16 having the rotor 5 fixed thereto by means of serrationrotates. According to this, the power is transmitted to the drum 3through the shaft 4, to rotate the drum 3.

In the meantime, performance of the foregoing drum type washing machinewill be described.

At first, since the tub 2 is formed of a heat resistant plastic, the tub2 is light, and since the tub 2 is injection molded, the tub 2 is easyto fabricate.

Since the bearing housing 7 is formed of a metal, such as an aluminumalloy, which shows little thermal deformation even at a hightemperature, the bearing housing 7 can be used in the drum type washingmachine having the spinning cycle.

Since the bearing housing 7 of metal is inserted in the hub of the tubrear wall at the time of injection molding of the tub 2 of plastic, toform an integrated type tub 2 and bearing housing 7, that permits todispense with the additional process of mounting the bearing housing 7on the tub rear wall, thereby simplifying the assembly process, andreduce an assembly man power.

Referring to FIG. 12, the recess 152 in the base part 150 of the stator6 reduces a stress in winding the core, thereby permitting an easy andsmall power winding.

Especially, referring to FIG. 13A, in the stator 6 having three or morethan three fastening parts 143 formed as a unit with the insulator so asto be projected in a radial direction toward inside from the insidecircumferential surface of the helical type core, each of the fasteningparts 143 is formed to meet a condition of a≧b, where “a” denotes alength of the tooth portion 151 from an outer edge of the base part 150,and “b” denotes a distance from an inner edge of the base part 150 to acenter of the fastening hole 143 a.

The condition is set taking a case into account, in which, even thoughthe closer the position of the fastening hole 143 a to a point a loadexerts thereon, the better in view of reduction of a torque, theposition of the fastening hole 143 a set at a position close excessivelyto the point a load exerts thereon leads to a bolt of smaller diameter,to require an excessively many number of bolts.

Referring to FIG. 13B, the fastening part 143 has a height greater than20% of a total core stack height, otherwise the fastening part 143 isliable to break due to vibration caused by motor driving. Especially,the fastening par 143 may have a height equal to or higher than thetotal core stack height.

However, because an excessively high fastening part 143 increases atotal width of the driving part, and reduces a washing capacity of thewashing machine, the height of the fastening part 143 is limited not toexceed two times of the total core stack height.

The cavity 143 c in the fastening part 143 dampens vibration at the timeof motor driving, to improve mechanical reliability of the stator 6.

The positioning pin 143 b on the fastening part 143 fits to thepositioning hole 710 b in the tub 2, thereby permitting an easy mountingof the stator 6 on the tub 2.

The sleeve form of bearing supporting part 7 a for supporting bearingsfitted therein, and the stator fastening part 7 b for fastening thestator 6 thereto, of the bearing housing 7, both of which are formed asa unit, can dispense with the related art tub supporter.

The boss 200 at a part of the tub rear wall opposite to each of thestator fastening holes 700 b prevents the stator fastening part 7 b fromcoming into direct contact with the stator 6, thereby preventing theinsulator of the stator 6 from being broken due to a fastening forceapplied thereto in mounting the stator 6.

The stepped areas 70 b-1 each having steps at preset intervals as thestepped area 70 b-1 extends in an outward radial direction of thecylindrical bearing supporting part 7 a, and the flat areas 70 b-2between adjacent stepped areas 70 b-1 and connected to the stepped areas70 b-1 in a circumferential direction with flat parts perpendicularthereto permit to increase bonding force to the tub 2 in the injectionmolding of the tub 2.

In addition to this, the circumferential rib 720 b at a position spaceda distance from an axis of the bearing supporting part 7 a alsoincreases a bonding force with the plastic in the injection molding ofthe tub 2.

Moreover, the through holes 730 b in the stator fastening part 7 bincreases the bonding force with the plastic in the insert injectingmolding of the bearing housing 7.

The fastening boss 70 b with the stator fastening hole 700 b in thebearing housing 7 can dispense with formation of fastening holes in thetub 2, additionally.

That is, according to the present invention, the stator 6 is fastened tothe stator fastening holes 700 b in the fastening boss 70 b of thestator fastening part 7 b buried in the tub rear wall with bolts.

The positioning hole 710 b formed adjacent to the stator fastening hole700 b of the stator fastening part 7 b in correspondence to apositioning projection on the insulator of the stator 6 improvesworkability in mounting the stator 6 on the tub rear wall.

Of course, the positioning hole 710 b in the stator fastening part 7 bis formed, not covered with plastic, but exposed, and in a case thepositioning hole is formed in the insulator, the positioning projectionwill be formed on the stator fastening part 7 b.

Since the front end of the shaft 4 is fixed to the spider 10 in the rearwall of the drum 3, and a section of the shaft 4 from a part exposed toan outside of the spider 10 to the front bearing 600 a has the brassbusing 11 forcibly press fit thereon, rusting of the shaft 4 isprevented.

The sealing member 12 on the outside surface of the bushing 11 preventsinfiltration of water toward the bearing.

The circumferential bent part with a seating surface 130 for seatingmagnets M placed on an inside surface of a side wall 13 b extendedforward from an edge of a rear wall of the rotor 5 permits an easyfabrication of the rotor since the seating surface 130 supports themagnet M easily when the magnet M is attached to the inside surface ofthe rotor 5.

The hub 132 in a center part of the rear wall 13 a having through holes131 permits to pass fastening members 15 a, such as bolts, in mountingthe rotor 5 on the shaft 4, and the plurality of radial cooling fins 133each with a length permits blowing of air toward the stator 6 to coolheat from the stator 6 when the rotor 5 rotates.

The cooling fin 133 is formed by lancing to direct an opened side of therotor 5, and a through hole 134 formed in the lancing serves as an airhole.

The rotor 5 formed of steel plate by pressing reduces a time periodrequired for fabrication of the rotor 5, and improves productivity.

The embossing 135 between adjacent cooling fins 133 on the rear wall 13a of the rotor 5 improves an overall strength of the rotor 5, and thedrain hole 136 in the embossing 135 permits to discharge water throughthe drain hole 136.

The connector 16, formed by a plastic injecting molding, has a vibrationmode different from a vibration mode of the rotor 5 of steel plate, toattenuate vibration transmitted from the rotor 5 to the shaft 4.

The serration 164 in the inside circumferential surface of the hub ofthe connector 16 engaged with the serration 400 in the rear end part ofthe shaft 4 enables transmission of a rotation power from the rotor 5 tothe shaft 4 through the connector 16 as it is.

FIG. 14 illustrates a perspective view of a stator in a driving part ofa drum type washing machine in accordance with another preferredembodiment of the present invention.

Referring to FIG. 14, the stator 6 of the present invention includes ahelical type core HC, an insulator 144 having the helical type core HCencapsulated therein, a coil wound on tooth portions 151 of the helicalcore HC, and fastening parts 143 formed as a unit with the insulator 144so as to be projected toward an inside of the helical type core HC.

That is, the stator 6 in the embodiment has, not a structure in whichthe fastening parts are projected in a radial direction toward an insideof the helical type core HC from more than three positions, but astructure in which the fastening parts form a unit with the insulator144 extended in a radial direction toward an inside of the helical typecore HC.

Alike the foregoing embodiment, the helical type core HC has multiplelayers formed by winding a steel plate in a helix starting from a bottomlayer to a top layer, with a plurality of tooth portions 151 projectedoutwardly in a radial direction from a base part 150 of the helical typecore HC, and recesses 152 in the base part 150 for reducing a stress inwinding the helical type core HC.

There is a positioning hole 143 g adjacent to the fastening hole 143 ain the fastening part 143, if there is a positioning pin on the tub rearwall, for fitting in mounting the stator. Opposite to this, of course,the positioning pin may be formed adjacent to the fastening hole 143 a,and the positioning hole may be formed in the tub rear wall.

Other parts and performances thereof of the embodiment are the same withthe foregoing embodiment, of which repetitive descriptions are omitted.

In the meantime, the present invention is not limited to aboveembodiments, it is of course possible that dimensions, shapes, andmaterials may be changed as far as the changes do not depart from thespirit or scope of the invention.

For an example, the stator fastening part 7 b may only have an outwardradial direction extension from the cylindrical bearing supporting part7 a with stepped areas 70 b-1 at preset intervals along a radialdirection. Or, alternatively, the stator fastening part 7 b may havealternate outward radial direction extensions from front part and rearpart of the cylindrical bearing supporting part 7 a in a circumferentialdirection connected at edges of the extensions substantiallyperpendicular to the extensions, without the stepped areas.

FIG. 15 illustrates a longitudinal section of a drum type washingmachine in accordance with another preferred embodiment of the presentinvention.

Referring to FIG. 15, the drum type washing machine includes a tub 2having a wall for holding washing water therein and mounting a drivingpart thereon, and a sleeve form of bearing supporting part 17 forsupporting bearings, in which both the tub 2 and the bearing supportingpart 17 are formed as one unit, a drum 3 rotatably arranged inside ofthe tub 2, a shaft 4 passed through the tub 2 and connected to the drum3 for transmission of a driving power from a motor to the drum, at leastone bearing 600 a inside of the bearing supporting part 17 forsupporting the shaft 4, a rotor 5 engaged to a rear end part of theshaft 4 to form the motor together with the stator 6, and the stator 6mounted on the tub 2 on an inner side of the rotor 5 and an outer sideof the bearing supporting part 17 with fastening members. The stator 6includes an annular helical type core HC having multiple layers formedby winding a steel plate having tooth portions 151 and base part in ahelix starting from a bottom layer to a top layer, an insulator havingthe helical type core HC encapsulated therein, a coil wound on the toothportions 151, and fastening parts formed as a unit with the insulator144, having fastening holes projected toward an inside of the helicaltype core HC for fastening to the bearing supporting part 17.

Of course, there are a plurality of fastening holes in an outer regionof the bearing supporting part 17 of the tub 2 for mounting the stator 6of motor with fastening members. There is a metal tube 143 p or a springpin forcibly inserted in the fastening hole 143 a of the fastening part143.

Both the tub 2 and the bearing supporting part 17 may be formed byplastic injection molding, or the tub 2 may be formed of plastic, andthe bearing supporting part 17 may be formed of a metal, such as analuminum alloy.

More preferably, in the plastic injection molding of the tub 2, the tub2 is injection molded in a state a tub supporting plate 18 of a metalformed as a separate piece from the bearing supporting part is buried inan outer region of the bearing supporting part 17.

Other parts not described herein are the same with the foregoingembodiment, and repetitive description of which will be omitted.

The performance of the embodiment will be described.

When a current flows to the stator 6, to rotate the rotor 5, the shaft 4connected to the rotor 5 rotates. The shaft 4 rotates supported on afront bearing 600 a and a rear bearing 600 b inside of the bearingsupporting part 17.

That is, a load on the shaft 4 is transmitted to the front, and rearbearings 600 a, and 600 b, and, therefrom, to the bearing supportingpart 17. Since the bearing supporting part 17 is formed as a unit withthe tub rear part, the bearing supporting part 17 can support the shaft4, more stably.

The tub supporting plate 18 of a metal formed as a separate piece fromthe bearing supporting part, and buried in an outer region of thebearing supporting part 17 in the injection molding of the tub 2 permitsto dispense with a separate reinforcing liner attached to the tub rearwall, enough to secure a supporting force for the stator 6 mounted onthe tub rear wall even if the BLDC motor is mounted on the tub walldirectly.

The drum type washing machine of the present invention has the followingadvantages.

First, the direct drive type motor reduces noise, out of order, andpower loss, and the bearing housing of a metal can be applied to aproduct with a drying function, as the bearing housing has no thermaldeformation.

Second, the rotor 5 of a steel plate formed by pressing reduces afabrication time period, and improves a productivity.

Third, the helical type core permits to reduce waste of material, easyfabrication, and increase a rigidity of the fastening part of the stator6 to reduce noise and vibration, and improve mechanical reliability, anda lifetime.

Fourth, the difference of vibration modes of the rotor and the connectorpermits to reduce vibration transmitted from the rotor to the shaft, andthe stator fastening part 7 b permits rigid mounting of the stator 6 onthe tub rear wall, and maintenance of concentricity of the stator 6,without damage of the tub rear wall.

Fifth, the elimination of tub supporter fitting work from the assemblyline permits to simplify an assembly process, and easy maintenance by aserviceman in repair and replacement of component.

Sixth, even if the BLDC motor with a net stator weight over 1.5 kg, anda rotation speed varied in a range of 0˜2000 RPM, or over is mounted onthe tub wall directly, the tub rear wall can support the stator,securely.

Referring to FIGS. 16 to 19, a bearing housing 7 of metal material isinserted into a rear wall of a tub according to the present invention.The tub 2 is injection-molded by injecting plastic melt thereto afterinserting the bearing housing into the tub 7.

A recessing part 120 and 220 and a projecting part 110 and 210 areformed on an inner surface or an outer surface of the rear wall of thetub 2. According to this embodiment of the present invention, theprojecting part 110 of the outer surface of the rear wall iscorresponding with the recessing part 220 of the inner surface thereof,whereas the recessing part 120 of the outer surface thereof iscorresponding with the projection part 210 of the inner surface thereof.That is, the rear wall of the tub 2 has an embossing appearance formedalong a circumferential direction. The above embossing appearance mayenable the rear wall of the tub 2 to secure enough strength andrigidity, even though the rear wall is not so thick.

The bearing housing 7 inserted into the rear wall of the tub 2 has aflange part 8. The flange part 8 is also insertedly formed in anembossing appearance corresponding with the embossing appearance of therear wall of the tub 2.

The circumferential ribs 121, 122, 123 and 124 and a radial rib 125 arecrossed on the recessing part 120 of the outer surface of the rear wallof the tub. Also, the circumferential ribs 221, 222, 223 and 224 and theradial rib 225 are crossed on the recessing part 220 of the innersurface of the rear wall.

The circumferential ribs 121 and 221 nearest to the center of the rearwall of the tub 2 are thicker than the other circumferential ribs.

Here, a circumferential rib 81 is formed on the recessing part of theflange part 8 of the bearing housing 7, corresponding with thecircumferential ribs 121˜124 and 221˜224 of the tub 2. Thecircumferential rib 81 of the flange part 8 is inserted into thecircumferential rib 121 and 221 nearest to the center of the tub 2.

Moreover, a boss 131 is formed on the rear wall of the tub 2 forfastening a stator 6 of a motor. The boss 131 is provided in thecircumferential rib 81 of the flange part 8, and a hole of the boss 131is exposed to the projecting part 110 of the outer surface of the rearwall.

The circumferential rib 121 and 221 nearest to the center out of thecircumferential ribs 121˜124 and 221˜224 is provided in the samecircumference as the circumference of the boss 131, such that the stator6 fastened to the boss 131 is supported securely.

The circumferential ribs 121˜124 and 221˜224 of the recessing part 120of the rear wall are spaced apart from an outer end of the flange part 8in a radial direction. A circumference referenced to as a dotted line‘A’ in FIGS. 16 and 17 is the portion where the outer end of the flangepart 8 of the bearing housing 7 is positioned, and the circumferentialribs 121˜124 and 221˜224 are not on the circumference, but spaced apartfrom the outer end of the flange part. Thus, stress is prevented frombeing concentrated only on some part enough to cause crack, because thecircumferential ribs 121˜124 and 221˜224 are not provided in the sameposition of the circumference of the outer end of the flange part 8.

Meanwhile, as shown in ‘B’ of FIG. 18, at least one portion of theradial rib 125 is inclined. The farther the radial rib is from thecenter, the higher the radial rib is inclined. As shown in FIG. 18, itis preferred that the inclined portion starts from the dotted ‘A’portion. Since the portion where the flange part 8 is not inserted,especially, the portion farther from the center of the rear wall isweaker in the strength and rigidity, the strength and rigidity of therear wall may be reinforced by heightening the rib.

The height of each circumferential rib 121˜124 and 221˜224 and theheight of each radial rib 125 and 225 are the same in most portionsthereof to prevent the stress from being concentrated only some part ofthe rear wall.

FIG. 19 illustrates a sectional view where the motor is mounted in therear wall of the tub 2. The stator of the motor is fastened to the boss131 of the rear wall of the tub 2 by a bolt, and a rotor 5 is connectedwith a shaft 4 and the shaft is connected with a drum 3.

Once the power is applied to the motor, the rotor 5 rotates to rotatethe shaft 4. Hence, the drum 3 rotates. Since the drum is vibratedduring the rotation, the vibration is transmitted to the rear wall ofthe tub through the shaft 4 and the bearing housing 7.

In case the number of rotor rotation is small due to the small capacityof the washing machine, the vibration of the drum 3 is also small.Thereby, the conventional rear wall of the tub is enough for thevibration. However, as recently the capacity of the washing machine hasbeen getting larger, the number of the motor rotation is larger. Thus,there have been demands for a tub 2 having a structurally strengthenedrear wall.

The rear wall of the tub 2 is invented through a process of trial anderror to cause no problems in a state where the capacity of the washingmachine is larger.

By the way, FIGS. 20 and 21 illustrate another embodiment of the presentinvention. Hereafter, only the different part from the above embodimentshown in FIG. 16 will be described.

Firstly, FIG. 20 illustrates an outer surface of a rear wall of a tub,and FIG. 21 illustrates an inner surface of the rear wall of the tub.

According another embodiment of the present invention, a circumferentialrib 111 and 211 and a radial rib 112 and 212 are crossed on a projectingpart 110 and 210. The ribs are provided on a circumference A where anouter end of a flange part 8 of a bearing housing 7 is provided.Thereby, the strength of the outer end of the flange part 8 of thebearing housing 7 may be reinforced.

In case that the circumferential rib 111 and 211 and the radial rib 112and 212 are formed on the projecting part 110 and 210, the enoughstrength may be reinforced even when the circumferential ribs 121˜124and 221˜224 formed on the recessing part 120 and 220 are provided on thecircumference A.

Therefore, according to the present invention, the problems which therelated art may cause will be solved.

Also, the rear wall of the tub injection-molded with the bearing housinginserted therein is structurally strengthened, because the recessingpart and projecting part are formed on the rear wall of the rub along acircumferential direction. Here, the flange part of the bearing housinghas the recessing part and the projecting part corresponding with therecessing part and the projecting part of the rear wall, such that therear wall of the tub may be more structurally strengthened.

Furthermore, the strength and rigidity of the rear wall may bereinforced due to the circumferential rib and the radial rib formed onthe rear wall of the tub. Especially, the ribs are formed on therecessing part. Thus, the thickness of the rear wall may be maintainedand there may not be any problems related to disposition of the othercomponents and tub capacity. Also, the rear wall of the tub may begained, because the inventor proved the correlation between thecircumferential rib position and the outer end of the flange part of thebearing housing.

The center portion of the rear wall affected by the vibration of theshaft may be structurally strengthened, because the circumferential ribnearest to the center of the rear wall is thicker than the othercircumferential ribs, thereby, shaft being supported securely to rotatethe drum smoothly.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. (canceled)
 2. A washing machine comprising: a cabinet; a tub made ofplastic within the cabinet to hold water therein and having a side walland a rear wall; a drum rotatably arranged in the tub; a shaft totransmit a driving power to the drum; a motor having a rotor and astator, wherein the rotor is coupled to the shaft and the stator is atthe rear wall of the tub; a bearing supporting part at a central portionof the rear wall of the tub holding a bearing to support the shaft; astator fastening part extending from the bearing supporting part in aradial direction and having a stator fastening hole to fasten thestator; and a plurality of through holes formed at the stator fasteningpart and filled with the plastic of the tub.
 3. The washing machine ofclaim 2, wherein at least one of the plurality of through holes iselongated.
 4. The washing machine of claim 2, further comprising aplurality of circumferential ribs formed on the stator fastening part.5. The washing machine of claim 4, wherein at least one through holeformed on the stator fastening part is between two circumferential ribs.6. The washing machine of claim 2, further comprising a circumferentialrib that includes a fastening boss corresponding to the stator fasteninghole of the stator fastening part.
 7. The washing machine of claim 6,wherein at least one of the plurality of through holes is between thecircumferential rib and a center of the stator fastening part.
 8. Thewashing machine of claim 2, further comprising a plurality of radialribs formed on the stator fastening part.
 9. The washing machine ofclaim 8, wherein at least one through hole formed on the statorfastening part is between two radial ribs.
 10. The washing machine ofclaim 2, further comprising a plurality of circumferential ribs and aplurality of radial ribs formed on the stator fastening part.
 11. Thewashing machine of claim 2, wherein the stator fastening part includesat least one stepped area.
 12. The washing machine of claim 2, whereinthe stator fastening part is bent at preset intervals.
 13. The washingmachine of claim 2, wherein the stator fastening part is a multi-leveledstructure.
 14. A washing machine comprising: a cabinet; a tub made ofplastic within the cabinet to hold water therein and having a side walland a rear wall; a drum rotatably arranged in the tub; a shaft totransmit a driving power to the drum; a motor having a rotor and astator, wherein the rotor is coupled to the shaft and the stator is atthe rear wall of the tub; a bearing supporting part holding a bearing tosupport the shaft at a central portion of the rear wall of the tub; astator fastening part extending from the bearing supporting part in aradial direction and having a stator fastening hole to fasten thestator; and a plurality of through holes formed on the stator fasteningpart, wherein an outer surface of the rear wall of the tub is locatedbetween the stator fastening part and the stator such that the throughholes are filled with the plastic of the tub.
 15. The washing machine ofclaim 14, wherein at least one of the plurality of through holes iselongated.
 16. The washing machine of claim 14, further comprising aplurality of circumferential ribs formed on the stator fastening part.17. The washing machine of claim 16, wherein at least one through holeformed on the stator fastening part is between two circumferential ribs.18. The washing machine of claim 14, wherein a circumferential ribincludes a fastening boss corresponding to the stator fastening hole ofthe stator fastening part.
 19. The washing machine of claim 18, whereinat least one of the plurality of through holes is between thecircumferential rib and a center of the stator fastening part.
 20. Thewashing machine of claim 14, further comprising a plurality of radialribs formed on the stator fastening part.
 21. The washing machine ofclaim 20, wherein at least one through hole formed on the statorfastening part is between two radial ribs.
 22. The washing machine ofclaim 14, further comprising a plurality of circumferential ribs and aplurality of radial ribs formed on the stator fastening part.
 23. Thewashing machine of claim 14, wherein the stator fastening part includesat least one stepped area.
 24. The washing machine of claim 14, whereinthe stator fastening part is bent at preset intervals.
 25. The washingmachine of claim 14, wherein the stator fastening part is amulti-leveled structure.